Method and control unit for loading a work tool of a work machine

ABSTRACT

A method for automated or automatic loading of a work tool of a work machine includes determining, as a function of operating conditions of the work machine, a probability of whether the work tool comes into or is in engagement with a material pile, and activating, in response to the determined probability being greater than a limit value, a load function for the automated or automatic loading. The method further includes ascertaining, when the load function is activated, a setpoint value for a lift position, a setpoint value for a tilt position, and a setpoint value for an accelerator pedal actuation as a function of a pressure measurement value on a hydrostat side of a power split transmission of the work machine, and ascertaining actuating signals for the automated or automatic loading as a function of a comparison of the ascertained setpoint values with corresponding actual values.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2019/085886, filed on Dec. 18, 2019, and claims benefit to German Patent Application No. DE 10 2019 200 079.7, filed on Jan. 7, 2019. The International Application was published in German on Jul. 16, 2020 as WO 2020/144018 A1 under PCT Article 21(2).

FIELD

The present disclosure relates to a method for loading a work tool of a work machine in an automated or automatic manner. The disclosure also relates to a control unit for carrying out said method.

BACKGROUND

The construction of a work machine having a power split transmission having a hydrostat is known from DE 10 2007 047 194 A1. A drive unit or drive machine is coupled to an input shaft of the power split transmission. The power split transmission has a hydrostatic branch and a mechanical branch, which are summed via a summation transmission embodied as a planetary gear transmission. The power split transmission provides at least two travel ranges in a forward travel direction and at least two travel ranges in a reverse travel direction. To this end, the power split transmission comprises a forward drive clutch and a reverse drive clutch, wherein the forward drive clutch and the reverse drive clutch are also referred to as reversing clutches. The travel ranges in the forward travel direction and the reverse travel direction are provided via gear clutches, also referred to as range clutches. The hydrostatic branch of the power split transmission comprises a hydrostat. The hydrostat is provided by a first hydrostatic unit and a second hydrostatic unit, wherein one hydrostatic unit acts as pump and the other hydrostatic unit acts as motor.

DE 10 2009 045 510 A1 discloses further details of a hydrostat, wherein this hydrostat also comprises two hydrostatic units. The hydrostatic units of the hydrostat interact with a position control valve. Hydraulic pressure can be applied to the hydrostatic units of the hydrostat via the position control valve in order to control them. A high-pressure regulating valve also interacts with the position control valve. Known is also a hydrostat that does not have such a high-pressure regulating valve but only has a position control valve.

It is also known from practice to install at least one pressure sensor in the region of the hydrostat of the power split transmission, in particular in a high-pressure region thereof, wherein the hydrostatic units of the hydrostat are acted upon and regulated, inter alia, as a function of the measurement value of the or of each pressure sensor.

DE 103 53 259 A1 or US 2004/0117092 A1 discloses a method for the automatic bucket loading of the bucket of a work machine, wherein the work machine can be a wheel loader. According to this prior art, a mass factor, a lift position, a tilt position, and a travel speed are detected metrologically as a function of corresponding sensors in order to generate actuating signals for lift actuator valves and tilt actuator valves as a function of these measurement signals and to thus automatically adjust the lift position and tilt position of the bucket for automatic bucket loading. The mass factor detected metrologically may be one or more of various machine parameters monitored to determine the extent of accumulation or mass formation of material piles. According to the prior art, a pressure in a lift and tilt hydraulic system of the bucket is detected and evaluated. For this purpose, sensors must be installed in the lift and tilt hydraulic system, which sensors determine the pressure and thus the load in the bucket. This is complex and therefore disadvantageous.

SUMMARY

In an embodiment, the present disclosure provides a method for automated or automatic loading of a work tool of a work machine. The work machine has a power split transmission having a hydrostat comprising hydrostatic units. The method includes determining, as a function of operating conditions of the work machine, a probability of whether the work tool of the work machine comes into or is in engagement with a material pile, and activating, in response to the determined probability being greater than a corresponding limit value, a load function for the automated or automatic loading of the work tool. The method further includes ascertaining, when the load function is activated, a setpoint value for a lift position of the work tool, a setpoint value for a tilt position of the work tool, and a setpoint value for an accelerator pedal actuation as a function of a pressure measurement value on a hydrostat side of the power split transmission, and ascertaining actuating signals for the automated or automatic loading of the work tool as a function of a comparison of the ascertained setpoint values with corresponding actual values.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:

FIG. 1 is a drive-side block diagram of a work machine having a power split transmission having a hydrostat;

FIG. 2 is a control-side block diagram of the work machine;

FIG. 3 is a block diagram illustrating a first aspect of a method;

FIG. 4 is a block diagram illustrating a second aspect of a method in a first variant;

and

FIG. 5 is a block diagram illustrating the second aspect of a method in a second variant.

DETAILED DESCRIPTION

The present disclosure provides a novel method for the automated or automatic loading of a work tool, such as a bucket of a work machine, such as a wheel loader, and a control unit for carrying out the method.

The probability of whether the work tool of the work machine comes into or is in engagement with a material pile is determined as a function of operating conditions of the work machine.

If the ascertained probability is greater than a corresponding limit value, a load function for the automated or automatic loading of the work tool is activated.

When the load function is activated, a setpoint value for a lift position of the work tool, a setpoint value for a lift position of the work tool, a setpoint value for a tilt position of the work tool, and a setpoint value for an accelerator pedal actuation are ascertained as a function of a pressure measurement value on the hydrostat side of the power split transmission.

Actuating signals for the automated or automatic loading of the work tool are ascertained as a function of a comparison of the ascertained setpoint values with corresponding actual values.

The method proposes to determine the probability of whether the work tool of the work machine comes into or is in engagement with a material pile. If the ascertained probability is greater than the corresponding limit value, the load function for the automated or automatic loading of the work tool is activated. When the load function is activated, the setpoint values for the automated or automatic loading of the work tool are ascertained as a function of the pressure measurement value on the hydrostat side of the power split transmission.

An external load acting on the work tool is accordingly ascertained not via sensors in a lift and tilt hydraulic system of the work tool but rather through the pressure measurement value of the hydrostat of the power split transmission directly at the power split transmission of the work machine. By the metrological detection of the external load acting on the work tool of the work machine directly at the power split transmission or directly in the hydrostat of the power split transmission, the external load can be ascertained easily and reliably with high accuracy without the need for pressure sensors in the region of the lift and tilt hydraulic system for the work tool.

The probability of whether the work tool of the work machine comes into or is in engagement with a material pile is preferably ascertained as a function of an actual value of the lift position of the work tool, as a function of an actual value of the tilt position of the work tool, and as a function of an actual value of an output rotational speed or an actual value of a gradient of the output rotational speed. In this way, the probability of whether the work tool of the work machine comes into or is in engagement with the material pile can be ascertained particularly advantageously.

If the pressure measurement value on the hydrostat side of the power split transmission is greater than the corresponding limit value when the load function is activated, the setpoint values for the automatic or automated loading of the work tool are automatically ascertained.

If the pressure measurement value on the hydrostat side of the power split transmission is greater than the corresponding limit value when the load function is activated, the setpoint value for the lift position of the work tool, the setpoint value for the tilt position of the work tool, and the setpoint value for the accelerator pedal actuation are ascertained. To this end, the setpoint value for the lift position as well as the setpoint value for the tilt position are in particular respectively increased, preferably until the pressure measurement value on the hydrostat side again drops below the corresponding limit value, and wherein subsequently, when the pressure measurement value on the hydrostat side again becomes greater than the corresponding limit value, the setpoint value for the lift position and the setpoint value for the tilt position are increased again. This is carried out until the setpoint value for the lift position as well as the setpoint value for the tilt position reach a corresponding limit value, i.e., until the work tool is maximally loaded.

The ascertained actuating signals are preferably used for automatically controlling the work machine in order to relieve an operator through the automatic loading of the work tool. Alternatively, the ascertained actuating signals are displayed in a display in order to assist an operator in the automated loading of the work tool.

The automatic control of the work machine is particularly preferred in order to completely relieve the operator. In this case, optimal loading results for the work tool can then be realized. However, even with the automated loading of the work tool, in which the actuating signals are only displayed in a display in order to assist the operator, the loading of the work tool of the work machine can be improved.

The actuating signals for the automated or automatic loading of the work tool are preferably also ascertained as a function of a measurement value of a weight sensor of the work tool and/or as a function of a measurement value of an output-side sensor of the work machine. The result of the loading of the work tool can thereby be further improved.

A method is provided for loading a work tool of a work machine, such as a bucket of a wheel loader, in an automated or automatic manner.

In such a work machine, a drive unit is coupled to an input shaft of a power split transmission. The power split transmission comprises a mechanical branch in addition to a hydrostatic branch into which a hydrostat is incorporated. The mechanical branch and the hydrostatic branch are summed or divided. The power split transmission can provide at least two travel ranges and thus gears both for a forward travel direction and for a reverse travel direction, wherein the power split transmission has reversing clutches and range clutches for this purpose. A pressure in the hydrostat, which comprises two hydrostatic units acting as a pump and a motor, can be monitored with at least one pressure sensor.

FIG. 1 schematically shows an exemplary block diagram of a work machine having a drive unit 2, a power take-out 1, an output 9, and a power split transmission 4 having a so-called secondary clutch. The power split transmission 4 comprises a hydrostat 5, which interacts with a planetary gear transmission 6 and a summation transmission 7, wherein the summation transmission 7 has gearwheel stages. The hydrostat 5 comprises the hydrostatic units acting as a pump and a motor. A reversing transmission 3 with the reversing clutches for changing between the forward travel direction and the reverse travel direction is connected on the drive side between the planetary gear transmission 6 and the drive unit 2 and the power take-out 1. A travel range transmission 8 with the range clutches for providing the at least two travel ranges is connected on the output side between the summation transmission 7 and the output 9. Drive power can be continuously provided on the output 9 within each travel range, as well as in the forward travel direction and in the reverse travel direction. The power split transmission 4 comprises the hydrostat 5, the planetary gear transmission 6, the summation transmission 7, the reversing transmission 3, and the travel range transmission 8. The actual power split takes place in hydrostat 5, planetary gear transmission 6, and summation transmission 7. Power take-out 1 may be a lift and tilt hydraulic system of a work tool, such as a bucket.

The above construction is familiar to the person skilled in the art and is known from DE 10 2007 047 194 A1 and from DE 10 2009 045 510 A1.

FIG. 2 shows a block diagram of control-side details of a work machine. FIG. 2 also shows the power split transmission 4, which comprises the hydrostat 5, which is operatively connected to the planetary gear transmission 6 and the summation transmission 7. With the aid of at least one pressure sensor (not shown) assigned to the hydrostat 5 of the power split transmission 4, a pressure in the high-pressure region of the hydrostat 5 and thus of the power split transmission 4 can be detected metrologically.

FIG. 2 furthermore shows a work tool 10 of the work machine, which is in particular a bucket. The work tool 10 can be raised and tilted via a lift and tilt hydraulic system or a lift frame, i.e., moved into a defined lift position and into a defined tilt position. In the lift frame, position sensors (not shown) are installed, with the aid of which actual values relating to the lift position as well as actual values relating to the tilt position of the work tool can be detected metrologically.

According to a first control-side variant of the work machine, it is possible for the work tool 10 of the work machine, namely the position sensors in the region of the lift frame of the work tool 10, to transmit actual values relating to the lift position of the work tool 10 as well as values relating to the tilt position of the work tool 10 in the direction of arrow 11 to the power split transmission 4, namely a control unit thereof. As a function thereof, i.e., as a function of these actual values of the lift position and of the tilt position, the power split transmission 4, namely the control unit thereof, ascertains actuating signals for controlling the work tool 10 and provides these actuating signals to a control unit 12 in the direction of arrow 13. The control unit 12 is a control unit of the lift frame of the work tool 10 of the work machine. According to arrow 14, the control unit 12 of the lift frame communicates with actuators of the lift frame of the work tool 10 in order to, in particular, transmit the actuating signals to the lift frame of the work tool 10 and to thus adapt the lift position of the work tool 10 and the tilt position of the work tool 10 via the actuators of the lift frame of the work tool 10.

FIG. 2 also shows an optional further control unit 15 of the work machine, wherein the data exchange or signal exchange can also take place via this further control unit 15. In the direction of arrow 16, the work tool 10 can thus provide the measurement values of the position sensors of the lift frame of the work tool 10 to the control unit 15, which then transmits in the direction of arrow 17 the corresponding measurement values via the actual value of the lift position of the work tool 10 and the actual value of the tilt position of the work tool 10 to the control unit of the power split transmission 4. The control unit of the power split transmission 4 then again ascertains actuating signals, which it transmits in the direction of arrow 18 to the further control unit 15, wherein the further control unit 15 provides these actuating signals to the control unit 12 in the direction of arrow 19. In contrast to a direct communication between the control unit of the power split transmission 4 and the control unit 12 of the lift frame in the direction of arrow 13, according to a second control-side variant, indirect communication in the direction of arrows 17, 18, and 19 can thus also take place, namely via the further control unit 15 of the work tool.

The present disclosure is concerned with loading a work tool of a work machine, preferably the bucket of a wheel loader, optimally in an automatic or automated manner, wherein the work machine comprises the power split transmission 4 having the hydrostat 5.

For automated or automatic loading of the work tool 10 of the work machine, a probability of whether the work tool 10 of the work machine comes into or is in engagement with a material pile is ascertained as a function of operating conditions of the work machine.

If this ascertained probability is greater than a corresponding limit value, a load function for the automated or automatic loading of the work tool 10 is activated.

When the load function is activated, a setpoint value for the lift position of the work tool 10, a setpoint value for the tilt position of the work tool 10, and a setpoint value for an accelerator pedal actuation of an accelerator pedal of the work machine are ascertained as a function of a pressure measurement value on the hydrostat side of the power split transmission 4 that is provided by a pressure sensor assigned to the hydrostat 5 in particular in the high-pressure region thereof.

As a function of a comparison of these ascertained setpoint values with corresponding actual values, actuating signals for the automated or automatic loading of the work tool 10 of the work machine are then ascertained.

FIG. 3 illustrates details for ascertaining the probability of whether the work tool 10 of the work machine comes into or is in engagement with a material pile. This probability is thus ascertained in a block 20 of FIG. 3, wherein a plurality of input variables 21, 22, and 23 are provided to the block 20 of FIG. 3 in which the probability of the engagement or impending engagement of the work tool 10 with a material pile is ascertained. Block 20 is thus provided with an actual value of the lift position of the work tool as the first input variable. As the second input variable 22, an actual value relating to the tilt position of the work tool is provided to the block 20. As a further input variable 23, an actual value of an output rotational speed or an actual value of a gradient of the output rotational speed is provided to the block 20. At least these three input variables 21, 22, and 23 are evaluated in order to ascertain the probability of whether the work tool 10 of the work machine comes into or is in engagement with a material pile.

If the actual value of the lift position of the work tool 10 according to the input variable 21, is in a first range, and if the actual value of the tilt position of the work tool 10 according to the input variable 22 is in a second range, and if the actual value of the output rotational speed according to the input variable 22 is smaller than a corresponding limit value, it is concluded that the probability of the work tool 10 of the work machine coming into or being in engagement with a material pile is greater than the corresponding limit value.

It is also possible that if the actual value of the lift position of the work tool 10 according to the input variable 21 is in the first range, and if the actual value of the tilt position of the work tool 10 according to the input variable 22 is in the second range, and if the actual value of the gradient of the output rotational speed is greater than a corresponding limit value, it is concluded that the probability of the work tool of the work machine 10 coming into or being in engagement with a material pile is greater than the corresponding limit value.

As a further input variable, a brake pedal position may optionally also be provided to block 20. When the brake pedal is actuated above the inch range, the probability of the work tool 10 of the work machine coming into or being in engagement with a material pile is low. Although the gradient of the output rotational speed as well as the output rotational speed change as such when the brake pedal is actuated, regular brake pedal actuation is not evaluated on the control side in that the probability of the work tool 10 coming into or being in engagement with the material pile is greater than the corresponding limit value.

If it is found in block 20 that the probability of the work tool 10 of the work machine coming into or being in engagement with a material pile is greater than a corresponding limit value, the system branches to block 24 and a so-called pile run is recognized. Branching to block 25 then takes place and the load function is activated for the automated or automatic loading of the work tool 10.

If, on the other hand, it is recognized in block 20 that the ascertained probability of whether the work tool 10 of the work machine comes into or is in engagement with a material pile is less than the corresponding limit value, branching to block 26 takes place and it is recognized that there is no pile run. In this case, branching to block 27 takes place and the load function remains inactive or is not activated.

Thus, if it is recognized that the probability of whether the work tool 10 comes into contact with or is in contact with a material pile is greater than the corresponding limit value, the load function for the automatic or automated loading of the work tool is activated.

When the load function is activated, namely if the pressure measurement value on the hydrostat side of the corresponding pressure sensor of the power split transmission 4 is greater than a corresponding limit value, the setpoint value for the lift position of the work tool 10, the setpoint value for the tilt position of the work tool 10, and the setpoint value for the accelerator pedal actuation are ascertained. These setpoint values are compared with the corresponding actual values in order to ultimately ascertain the actuating signals for the automated or automatic loading of the work tool 10 as a function thereof.

FIG. 4 illustrates details of a load function that generates actuating signals for an automated loading of the work tool 10. FIG. 4 shows input variables for the load function, namely an input variable 28 of the pressure measurement value on the hydrostat side, an input variable 29 of the actual value of the lift position of the work tool 10, an input variable 30 of an actual value of the tilt position of the work tool 10, and an input variable 31 of an actual value of the accelerator pedal, and another optional input variable 32 of an actual value of the output rotational speed via which the pressure measurement value on the hydrostat side of the power split transmission 4 can be validated.

According to FIG. 4, on the basis of these input variables, the control unit of the power split transmission 4 ascertains on the one hand the above setpoint values and on the other hand, as a function of the comparison of the above setpoint values with the corresponding actual values, actuating signals, which the control unit of the power split transmission 4 provides to the further control unit 15 of the work machine, wherein the further control unit 15 of the work machine displays the corresponding actuating signals in or on a display 33 of the work machine in order to assist the operator of the work machine in the automated loading of the work tool 10.

FIG. 4 shows, over the time t, different indications on the display 33 which serve to assist the operator in the loading of the work tool 10. Different actuating signals are thus displayed on the display 33, namely an actuating signal about the tilting of the work tool 10 as a first actuating signal, an actuating signal about lifting or lowering of the work tool 10 as a second actuating signal, and an actuating signal about an accelerator pedal actuation as a third actuating signal. It is thus always known to the operator which actions he has to perform for optimally loading the work tool 10. The operator thus continuously receives over the time t information as to whether the has to further tilt or further lift the work tool 10 as well as information as to whether the actuation of the accelerator pedal is OK or whether the accelerator pedal has to be actuated more strongly, or whether the accelerator pedal has to be released and thus actuated less strongly.

FIG. 5 illustrates details of an activated load function that, in contrast to FIG. 4, serves not for the automated loading of the work tool 10 but rather for the automatic or fully automatic loading of the work tool 10 of the work machine. Here again, various input variables 28, 29, 30, 34, and 32 are used, wherein the input variable 28 is again the pressure measurement value of the power split transmission 4, namely the pressure measurement value on the hydrostat side of a corresponding pressure sensor, wherein the input variable 29 is the actual value of the lift position of the work tool 10 and the input variable 30 is the actual value of the tilt position of the work tool 10. The input variable 34 is an actual value of a brake pedal actuation, and the optional input variable 32 is the output rotational speed.

These input variables are provided to the control unit of the power split transmission 4, which then, as described above, generates the actuating signals as a function of ascertained setpoint values and a comparison of these setpoint values with corresponding actual values, and provides the corresponding actuating signals to the control unit 12 of the lift frame either directly in the direction of arrow 13 or indirectly in the direction of arrows 17, 19 via the further control unit 15 of the work machine.

The control unit 12 of the lift frame then uses these actuating signals for automatically controlling the work machine in order to relieve the operator through the automatic loading of the work tool. The adjustment of the lift position and of the tilt position and the accelerator pedal actuation then takes place fully automatically on the basis of the ascertained actuating signals.

In the case of an actuation of the brake pedal by the operator, which is provided to the control unit of the power split transmission 4 as an input variable 34, an automatic termination of the automatic loading of the work tool 10 takes place. For the subsequent activation of the load function, a probability for a pile run which is greater than the corresponding limit value has to be ascertained again. Thus, a probability of the work tool 10 coming into or being in engagement with a material pile must be ascertained again.

Through the continuous monitoring or measurement of the pressure measurement value on the hydrostat side, an optimal lift position and tilt position for the work tool 10 and an optimal accelerator pedal actuation can be ascertained continuously in order to optimally load the work tool 10.

Provision can be made for the actuating signals for the automated or automatic loading of the work tool 10 to be also ascertained as a function of a measurement value of a weight sensor of the work tool 10 and/or as a function of a measurement value of an output-side sensor of the work machine. If, for example, it is found that the weight of the work tool 10 has already exceeded a limit value, the loading process can be terminated. The limit value can be predefined in a manner selectable via an HMI interface since different materials have different densities.

If spinning wheels of the work machine 10 are recognized on the basis of a measurement value of an output-side sensor, the accelerator pedal actuation can be reduced in order to prevent the surface to be traveled on from being damaged as a result of spinning wheels. If spinning wheels are recognized, an accelerator pedal actuation is reduced and the work tool 10 is preferably additionally lifted more strongly. Subsequently, further loading of the work tool 10 can take place via a renewed accelerator pedal actuation.

In the automatic loading of the work tool 10, the efficiency of the loading of the work tool 10 can be further increased by means of a LEM algorithm, which ascertains an optimal amount of the loading of the work tool 10 over a plurality of automatic loading processes.

The present disclosure furthermore relates to a control unit of a work machine which is configured to carry out the method described above. This control unit is, in particular, the control unit of the power split transmission 4, which on the one hand ascertains the probability of a pile run on the basis of the above-described variables, and which on the other hand automatically activates the load function if the probability of a pile run is greater than the corresponding limit value and then ascertains the actuating signals for the automatic or automated loading of the work tool 10 as a function of the other input variables described above.

This control unit has hardware-side means and software-side means for carrying out the method described above. The hardware-side means include data interfaces in order to exchange data with assemblies involved in the execution of the method, in particular with the sensors providing the required input variables. Furthermore, these hardware-side assemblies include a processor for data processing and a memory for data storage. Software-side means include program modules for performing the method.

The control unit is part of a control system of the work machine. The control unit, or the control system, is part of the work machine.

While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.

The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

LIST OF REFERENCE SIGNS

-   1 Power take-out -   2 Drive unit -   3 Reversing transmission -   4 Power split transmission -   5 Hydrostat -   6 Planetary gear transmission -   7 Summation transmission -   8 Travel range transmission -   9 Output -   10 Work tool/lift frame -   11 Arrow -   12 Control unit of the work tool/lift frame -   13 Arrow -   14 Arrow -   15 Control unit of the work machine -   16 Arrow -   17 Arrow -   18 Arrow -   19 Arrow -   20 Probability determination -   21 Actual value of the lift position -   22 Actual value of the tilt position -   23 Actual value of the output rotational speed/output rotational     speed gradient -   24 Pile run recognition -   25 Load function activation -   26 No pile run recognition -   27 No load function activation -   28 Pressure measurement value on the hydrostat side -   29 Actual value of the lift position -   30 Actual value of the tilt position -   31 Actual value of the accelerator pedal actuation -   32 Actual value of the output rotational speed -   33 Display -   34 Actual value of the brake pedal actuation 

1. A method for automated or automatic loading of a work tool of a work machine, wherein the work machine has a power split transmission having a hydrostat comprising hydrostatic units, the method comprising: determining, as a function of operating conditions of the work machine, a probability of whether the work tool of the work machine comes into or is in engagement with a material pile; activating, in response to the determined probability being greater than a corresponding limit value, a load function for the automated or automatic loading of the work tool; ascertaining, when the load function is activated, a setpoint value for a lift position of the work tool, a setpoint value for a tilt position of the work tool, and a setpoint value for an accelerator pedal actuation as a function of a pressure measurement value on a hydrostat side of the power split transmission, and ascertaining actuating signals for the automated or automatic loading of the work tool as a function of a comparison of the ascertained setpoint values with corresponding actual values.
 2. The method according to claim 1, wherein determining the probability of whether the work tool of the work machine comes into or is in engagement with a material pile is determined as a function of an actual value of the lift position of the work tool, as a function of an actual value of the tilt position of the work tool, and as a function of an actual value of an output rotational speed or as a function of an actual value of a gradient of an output rotational speed.
 3. The method according to claim 2, wherein if when the actual value of the lift position is in a first range, the actual value of the tilt position is in a second range, and if-either the actual value of the output rotational speed is less than a corresponding limit value or the actual value of the gradient of the output rotational speed is greater than a corresponding limit value, the probability is determined to be greater than the corresponding limit value.
 4. The method according to claim 1, wherein the setpoint value for the lift position of the work tool, the setpoint value for the tilt position of the work tool, and the setpoint value for the accelerator pedal actuation are ascertained when the pressure measurement value on the hydrostat side of the power split transmission is greater than a corresponding limit value when the load function is activated.
 5. The method according to claim 1, further comprising displaying, in a display, the actuating signals in order to assist an operator in automatically loading the work tool.
 6. The method according to claim 5, wherein a first actuating signal indicates to the operator a tilting of the work tool, a second actuating signal indicates a lifting or lowering of the work tool, and a third actuating signal indicates an accelerator pedal actuation.
 7. The method according to claim 1, wherein the actuating signals are used for automatically controlling the work machine in order to relieve an operator through the automatic loading of the work tool.
 8. The method according to claim 7, wherein the automatic loading of the work tool is terminated by brake pedal actuation.
 9. The method according to claim 1, wherein the actuating signals for the automated or automatic loading of the work tool are ascertained as a function of a measurement value of a weight sensor of the work tool and/or as a function of a measurement value of an output-side sensor of the work machine.
 10. A control unit of a work machine the control unit being configured to carry out the method according to claim
 1. 11. The method according to claim 1, wherein the work machine is a wheel loader and the working tool is a bucket of the wheel loader. 